morality is subjective, there is no absolutely right or wrong answer...marriage is ultimately a relationship that holds a status in our society as sacred, therefore making it easy for others to pass "judgment". those are the people who need to ask themselves, "do i have any right to judge another?"

This isn't much of a philosophical question without at least some rudimentary arguments being thrown back and forth. Why exactly do you believe moral zealots look down upon fornication outside of marriage? What types of marriage qualify? What are their presuppositions? How can they be attacked and undermined, rather than dismissed intuitively?

1. Moral zealots would look down upon fornication because of practical considerations - a greater chance of unwanted pregnancies, STDs and a perceived breakdown of societal structure - in theological clothes.

4. These would be attacked and undermined by the history of "abnormal" relationships practiced by the majority of society, and by marriage being primarily a religious and moral contract (violated by a majority under such), vs a biological and pleasurable imperative.

I think the answer to the OP depends on the definition of fornification. Are we talking about procreation or just individual sexual pleasure ? If the first, then only heterosexual fornification can be moral, if the second, then both heterosexual and homosexual activities would be equally moral.